You MITB looks great. I made one last year using the specs from this site and a copy of Zombie's cam, but I had troubles getting a motor to lift the lid. Even after I replaced the lid with luan plywood and 1/2" foam "boards", the motor would fail to lift it.
I noticed you are using a wiper motor. Has anyone else used this method? I have a wiper motor in my witches cauldron, but I thought the speed (41 RPM) would be way too fast for this prop.
Also, are there any surplus sites on the internet where you can buy a high torque, low RPM motor for a good price?
A stronger motor or a lighter material for the lid would be ideal. This is a problem I ran into when I built mine. I went with a thinner plywood for the lid and it was still too heavy for my motor so I had to "obtain" a motor that would provide more torque.
I can see the problem is you've used dimensional lumber to build the entire lid. Plywood would be more ideal because it's thinner and thus, lighter as well. You could always use a router to hollow out the bottom side of the lid, but I think you'd lose too much structural integrity and the lid would eventually break under the stress of always opening and slamming shut.
The motor I used is described in detail in my how-to. It was a rather expensive motor (that I was able to get a free sample from my company) but it has the right RPM and can lift the rod with enough effort to get the job done. However, I suspect that even the motor I used wouldn't be powerful enough to lift your lid as it is.